Risk factors for drug resistant TB in British Columbia

Objectives: A) To investigate the epidemiological risk factors associated with resistance to antituberculosis drugs in British Columbia B) To determine if there are differences in risk factor characteristics among different categories of drug resistant (mono-drug, poly and multi-drug resistance) TB cases. Methods: The study was carried out in two phases. The first phase of the study was retrospective in design. The data examined in this study was collected by the division of TB control of British Columbia and was obtained from retrospective review of charts, prescriptions, files of the TB subjects or other clients who attended the provincial (BC) TB service. The second phase involved a matched case control study design (using a sample from the total study population). Cases were all resistant TB subjects while controls were selected randomly from the pool of sensitive subjects matched on age group and sex. Results: A total of 3041 TB subjects were eligible for this study over a period of 12 years (1990- 2001). Of those eligible, there were 295 (10%) resistant cases and 2746 (90%>) sensitive cases. The significant risk factors for drug resistance found in this study were immigration status, ethnicity, birth country, last country of residence, a history of previous TB, place of diagnosis and case category. With respect to immigration, foreign born people are four times more likely to present with drug resistance than the Canadian-born people. Among the ethnic groups, Chinese, Southeast Asian and the Rest of the Asian are two to three times more likely to present with drug resistance than Caucasians. According to birth country, people born in China, Southeast Asia, and other parts' of Asia were four times more likely to present with drug resistance than Canadian-born people. Subjects with a history of previous TB were twice as likely to present with drug resistance compared to the subjects without any history of previous TB. Subjects diagnosed outside of Canada were almost three times more likely to have drug resistance compared to the subjects diagnosed in Canada. Reactivated (relapsed) cases are almost three times as likely to present with drug resistance compared to the new cases. Conclusions: In brief, foreign born immigrants, patients with a history of previous TB and reactivated (relapsed) TB cases are at greater risk for TB drug resistance. Efforts should be made to prioritize the development and implementation of effective screening and treatment protocols for these high risk groups in order to avoid the emergence of further resistance tuberculosis.Medicine, Faculty ofPopulation and Public Health (SPPH), School ofGraduat